record.java

j2me下的1套UI框架.包含j2me开发中会应用的各种低级组件

package com.jmobilecore.dstore;

/**
 * A <code>Record</code> represents a database record
 *
 * @author 	Greg Gridin
 */
public class Record {

    /**
     * The maximum size for the record's data
     **/
    public static int MAX_SIZE = 1024;

    /**
     * The <code>RecordStructure</code> for the current <code>Record</code>
     **/
    public RecordStructure struct;

    /**
     * The data for the current <code>Record</code>
     **/
    public byte[] data;

    /**
     * The length of the data
     **/
    public int length;

    /**
     * Creates an <code>Record</code> instance
     * @param  rStructure the <code>RecordStructure</code> for the record.
     **/
    public Record(RecordStructure rStructure) {

        struct = rStructure;
        data = new byte[MAX_SIZE];
        if (rStructure == null) return;
        reset();
    }

    /**
     * Creates an <code>Record</code> instance
     * @param  rStructure the <code>RecordStructure</code> for the record.
     * @param  data the input data for the record.
     **/
    public Record(RecordStructure rStructure, byte[] data) {

        struct = rStructure;
        this.data = data;
        calcLength();
    }

    protected void calcLength() {
        if (struct == null) {
            length = 0;
            return;
        }
        int numFields = struct.fieldStructure.size();
        FieldStructure fStruct;
        int newLength = numFields * 4;
        for (int i = 0; i < numFields; i++) {
            fStruct = struct.getFieldStructure(i);
            if (FieldStructure.hasVariableLength(fStruct.type)) {
                int desc = getDescriptor(i);
                if (desc == FieldStructure.NULL) continue;
                int offset = desc >>> 16;
                int len = (desc & 0x0000ffff);
                if (newLength < offset + len) newLength = offset + len;
            }
        }
        length = newLength;
    }

    /**
     * The buffer used for current <code>Record</code> compacting
     **/
    static protected Record buffer = new Record(null);

    protected void compact() {

        synchronized (buffer) {
            buffer.struct = struct;
            int newOffset = struct.descLength;
            FieldStructure field;
            int desc, curOffset, curLength;
            for (int i = 0; i < struct.fieldStructure.size(); i++) {
                field = struct.getFieldStructure(i);
                desc = getDescriptor(i);
                if (!FieldStructure.hasVariableLength(field.type) || desc == FieldStructure.NULL) {
                    buffer.setDescriptor(i, desc);
                    continue;
                }
                curOffset = desc >>> 16;
                curLength = (desc & 0x0000ffff);

                buffer.setDescriptor(i, newOffset << 16 | curLength);
                if (curLength<=0) continue;
                System.arraycopy(data, curOffset, buffer.data, newOffset, curLength);
                newOffset += curLength;
            }
            if (data.length < newOffset) {
                data = new byte[MAX_SIZE];
            }
            System.arraycopy(buffer.data, 0, data, 0, newOffset);
            length = newOffset;
        }
    }

    /**
     * Sets specified column to <code>byte[]</code> value
     * Compacts storage if necessary
     * @param  fIndex the field index.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field index was given
     * @exception ArrayStoreException  if an invalid value cannot be stored in <code>Record</code>
     * @see FieldStructure#NULL
     **/
    protected void setBinaryData(int fIndex, byte[] value, int offset, int numBytes) {

        if (!FieldStructure.hasVariableLength(struct.getFieldStructure(fIndex).type)) {
            return;
        }
        int curOffset = length, curLength = 0;
        int desc = getDescriptor(fIndex);
        if (desc != FieldStructure.NULL) {
            curOffset = desc >>> 16;
            curLength = (desc & 0x0000ffff);
        }
        if (numBytes==0) {
            setDescriptor(fIndex, curOffset << 16 | numBytes);
            return;
        }
        int dynamicSize = data.length - length - (numBytes - curLength);
        if (dynamicSize < 0) {
            compact();
            desc = getDescriptor(fIndex);
            if (desc == FieldStructure.NULL) curOffset = length;
            else curOffset = desc >>> 16;
            dynamicSize = data.length - length - (numBytes - curLength);
        }
        if (dynamicSize < 0) {
            throw new ArrayStoreException();
        }
        setDescriptor(fIndex, curOffset << 16 | numBytes);
        if (curOffset != length) {
            if (curLength < numBytes) {
                compact();
                desc = getDescriptor(fIndex);
                curOffset = desc >>> 16;
            }
        }
        else {
            length += numBytes - curLength;
        }
        System.arraycopy(value, offset, data, curOffset, numBytes);
    }

    /**
     * Sets specified column to <code>byte[]</code> value
     * @param  fName the field name.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field name was given
     * @see FieldStructure#NULL
     **/
    public void setBinaryField(String fName, byte[] value, int offset, int numBytes) {
        setBinaryField(struct.getFieldNum(fName), value, offset, numBytes);
    }

    /**
     * Sets specified column to <code>byte[]</code> value
     * @param  fIndex the field index.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field index was given
     * @see FieldStructure#NULL
     **/
    public void setBinaryField(int fIndex, byte[] value, int offset, int numBytes) {
        if (value == null) {
            setNull(fIndex);
            return;
        }
        setBinaryData(fIndex, value, offset, numBytes);
    }

    /**
     * Sets specified column to <code>String</code> value
     * @param  fName the field name.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field name was given
     * @see FieldStructure#NULL
     **/
    public void setStringField(String fName, String value) {
        setStringField(struct.getFieldNum(fName), value);
    }

    /**
     * Sets specified column to <code>String</code> value
     * @param  fIndex the field index.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field index was given
     * @see FieldStructure#NULL
     **/
    public void setStringField(int fIndex, String value) {
        if (value == null) {
            setNull(fIndex);
            return;
        }
        byte [] data = value.getBytes();
        setBinaryData(fIndex, data, 0, data.length);
        data = null;
    }

    /**
     * Sets specified column to <code>boolean</code> value
     * @param  fName the field name.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field name was given
     * @see FieldStructure#NULL
     **/
    public void setBooleanField(String fName, boolean value) {
        setBooleanField(struct.getFieldNum(fName), value);
    }

    /**
     * Sets specified column to <code>boolean</code> value
     * @param  fIndex the field index.
     * @param  value the field value.
     * @exception IndexOutOfBoundsException  if an invalid field index was given
     * @see FieldStructure#NULL
     **/